Phone slow

I have Samsung Galaxy Ace 3 S7275R and a Samsung Galaxy Grand Neo i9060 mobile phones and the
first one is slow because of some apps i installed. The free memory is only 170-250MB. It was fast and with 350MB free ram before. I installed the same apps on the second phone and this phone it has 450MB Ram left and is fast. Both phones have 1 GB Ram, 1200mhz cpu and are almost identical except the second phone
is quad-core while the first is double-core. Why this is happening and some phones are fast and others are
slow on Samsung phones like this happening to my first phone while in the second the speed is ok? If it is
the firmware then do you know of a original firmware name i can download that has better free and is
optimized for better performance? Give me with firmware version code and country. I currently flashed
with Odin a 8.3.2016 Samsung firmware firmware for Netherlands but the speed is the same. What should i do?